Embedded Android devices are multifunctional and can be adapted to a wide variety of potential applications. Here are three embedded Android devices currently on the market.

With the availability of cheap flash media, energy-efficient and abundant ARM processors, and the practically zero cost of Android, a new type of product has emerged in the marketplace: embedded Android devices. While Android is certainly familiar on phones and tablets, these devices are rather multifunctional and can be adapted to a wide variety of potential applications, such as public internet terminals, digital signage, video players, and much more.
Sanoxy MK808
The lack of available ports can be somewhat limiting, but that can be corrected with a USB hub. The current version of Android for the MK808 is 4.2.
Pivos XIOS DS
Somewhat secondary to being an embedded Android device, Pivos is marketing it primarily as a video player, with a custom distribution of XBMC, which is optimized to use hardware decoding, though they insist that XBMC support is presently in beta. Additionally, the XIOS DS is still on Android 4.0 (Ice Cream Sandwich), not Jelly Bean.
HardKernel ODROID-XU
The ODROID-XU has a Samsung Exynos 5 CPU, which is one of the first commercially available ARM “big.LITTLE” CPUs: It contains a quad-core ARM Cortex-A15 at 1.6 GHz, and a quad-core Cortex-A7 1.2 GHz in one package. Alongside that is a PowerVR SGX544MP3 GPU, 2GB LPDDR3 RAM, 10/100 Ethernet, 4 USB 2.0 host ports, 1 USB 3.0 host port, 1 USB OTG port, microHDMI output, and for storage, microSDHC or eMMC 4.5. It also has 30 I/O pins for various uses. Of note, 802.11 b/g/n Wi-Fi is available only as a USB module, though there’s clearly no real shortage of those.
The ODROID-XU currently runs Android 4.2.2 and Ubuntu Server 13.04 with only console output. Older ODROID devices have support for Ubuntu but in a way that isn’t quite hardware-optimized, and according to HardKernel, the major impediment in Linux support now is the HDML/LCD driver for X.Org. Further updates will occur in Q4 2013.
Quick comparison: Raspberry Pi
The Raspberry Pi is a very neat device and great educational tool, but in fairness, it isn’t that great at running Android. The Pi has a single-core 700 MHz ARM processor and 512 MB of RAM. It's quite capable of running minimal Linux distributions, RISC OS, and even the open-source BeOS offshoot Haiku, but Android may well be a bit too resource-intensive for it. The Raspberry Pi definitely has cost working in its favor -- at $25 or $35 (USD) depending on the model. So, if you’re not tied to Android, it’s definitely worth a look.
Conclusion
Buy according to your need. If you need to be pushing a lot of pixels or crunching a bunch of numbers on a small board running Android, the ODROID-XU is the product for you. If you want to watch Netflix on your TV or run a video streaming app in a public place, the MK808 can accomplish that for you with ease and within budget.